2018-02-21T05:41:56ZSpatial variation, bias and experimental design in agronomic field trials: a case study of a farming systems trial in the Western Cape province, South Africahttp://scholar.sun.ac.za:80/handle/10019.1/102963
Spatial variation, bias and experimental design in agronomic field trials: a case study of a farming systems trial in the Western Cape province, South Africa
Osborne, Devin Guy
ENGLISH SUMMARY: Detecting small statistically significant changes in an observed parameter (e.g. – yield) in response to
applied treatments within field trials is a major challenge for modern agriculture, since we continue
looking for smaller increments where spatial variability (noise) may obscure the sought trend. A reliable
detection of change can significantly reduce the length of some long-term trials required for a trend
confirmation.
This study assesses the effects of spatial variation in yield, terrain and soil properties within a long-term
field trial on the possible outcome of results. The experiment was set up at the Langgewens research farm
of the Western Cape Department of Agriculture, South Africa as an extension of the long-term trial
initiated by the provincial government. In year 1 (2015) the whole field was planted to wheat as a
uniformity trial to assess the magnitude of productivity, variation and spatial trends within the 12 ha
experimental site. A yield monitor mounted on a combine harvester and remote sensing techniques using
drone surveys were used to study the variability in wheat growth/yield, and topographic parameters
within the field trial area. Soil profiles positioned along the field perimeter were interpolated into a soil
map to understand some of the reasons for yield variability. The relationship between topographic
parameters and wheat yield was significantly more important in the drier year (2015) than in 2016. Results
from a random forest regression model indicated that the use of spectral vegetation indices NDVI and
SAVI, in combination with topographic parameters can be used to accurately predict wheat yield in dry
and in wet years (R2 = 0.974 and R2= 0.987 respectively).
Wheat growth and productivity during the uniformity trial showed high variation within the trial area
(1.46±0.61 t·ha-1) with a bimodal distribution largely determined by variation in topography and soil types.
The first step in trial layout optimization was the exclusion of a small low-yielding area on the eastern
margin retaining the bimodal distribution, but slightly increasing the mean and significantly reducing the standard deviation (1.68±0.46 t·ha-1). The reduced-area experimental setup comprises 120 plots
combining three main 10-year crop rotation treatments starting at a different year of rotation resulting in
k=30 x n=4 trial for each year and finally combining into k=3 x n=40 at the end of the trial period.
Soil core samples at a 0-5cm depth (120 in total) were analysed for some key soil parameters. The variation
in routinely analysed soil properties across the field within the 0-5cm layer, where the most changes may
be expected as a result of applied treatments collectively showed no effect on wheat productivity. The
only exception was the resistance measurements, which indicated a high degree of leaching negatively
correlated with wheat production.
The trial was further optimized for means by complete randomization of the trial setup by placing three
treatment replicates in the high-yielding block and the fourth replicate in the lower-yielding part of the
field. This resulted in a relatively uniform distribution of means and standard deviations across the trial.
Such setup also allowed the possibility of replication reduction to n=3 (or n=30 at the end of the trial) by
excluding the lower-yielding section. The supposition that reduction of replications under the
circumstances may lower the difference was supported by power analysis. The power analysis of the 2015
yield has shown that three replications within a more uniform field allow for detection of smaller changes
(160 kg·ha-1) as opposed to highly variable conditions with 4 replications (314 kg·ha-1).
A different approach – optimization for within-treatment standard deviation was realized by quantifying
and accounting for the spatial trend. The combination of replications into ranked groups results in
significant reduction of within-group standard deviation and, subsequently smaller detectable
differences. This approach should be further investigated in the time-series analysis as the current
experiment progresses.
Thesis (MScAgric)--Stellenbosch University, 2017.
2017-12-01T00:00:00ZSoil moisture conservation in dryland viticulture as affected by conventional and minimum tillage practiceshttp://scholar.sun.ac.za:80/handle/10019.1/101879
Soil moisture conservation in dryland viticulture as affected by conventional and minimum tillage practices
Van Huyssteen, L.; Weber, H. W.
The effect of conventional clean cultivation, a straw mulch, chemical weed control and a grass sward on the soil moisture regime in a dryland vineyard was investigated. The results demonstrate that both a straw mulch and chemical weed control were very effective ju conserving winter-stored soil moisture until mid- or even late summer to support the vines during the almost rainless growing season. Further, it appeared that a mere loosening of the soil surface periodically by way of clean cultivation cannot conserve soil moisture effectively; it may, on the contrary, promote evaporation in the top-soil layers, especialzy when done after rain. On the other hand, an undisturbed soil surface, as in the case of chemical weed control, acts as a mulch in itself after the surface layer has dried out, thus reducing evaporation. Even under conditions of frequent rainfall, as during the first part of 1976/77 season, the straw mulch cover treatment was still superior to all other treatments in conserving soil moisture.
CITATION: Van Huyssteen, L. & Weber, H. W. 1980. Soil moisture conservation in dryland viticulture as affected by conventional and minimum tillage practices. South African Journal of Enology & Viticulture, 1(2):67-75, doi:10.21548/1-2-2415.; The original publication is available at http://www.journals.ac.za/index.php/sajev
1980-01-01T00:00:00ZThe effect of conventional and minimum tillage practices on some soil properties in a dryland vineyardhttp://scholar.sun.ac.za:80/handle/10019.1/101874
The effect of conventional and minimum tillage practices on some soil properties in a dryland vineyard
Van Huyssteen, L.; Weber, H. W.
Preliminary results of a long-term viticultural tillage experiment comprising two groups of treatments, are reported. These groups are (i) a group of "minimum" tillage practices having received no mechanical soil tillage at all, and (ii) a group of "conventional" tillage treatments according to long-established local practices by disc-harrow. The "minimum" group consists of: (a) a permanent straw mulch cover, (b) chemical weed control, and ( c) a permanent cover of indigenous weeds frequently cut by a bush-cutter. The "conventional" group consists of: (a) deep and (b) shallow trench furrow systems, and (c) the locally customary "clean cultivation" system. A comprehensive investigation into the changes of sleeted soil properties after a period of eight years revealed significant differences between properties of the soil under minimum tillage (group (i)) and under clean cultivation (group (ii)). Soil parameters, such as pore volume distribution, compaction indices, activity of micro-organisms and availability of plant nutrients, were found to be more favourable in some minimum tillage treatments than on the conventionally tilled plots.
CITATION: Van Huyssteen, L. & Weber, H. W. 1980. The effect of conventional and minimum tillage practices on some soil properties in a dryland vineyard. South African Journal of Enology & Viticulture, 1(1):35-45, doi:10.21548/1-1-2412.; The original publication is available at http://www.journals.ac.za/index.php/sajev
1980-01-01T00:00:00ZThe effect of various supplementary irrigation treatments on plant and soil moisture relationships in a vineyard (vitis vinif era var. chenin blanc)http://scholar.sun.ac.za:80/handle/10019.1/101872
The effect of various supplementary irrigation treatments on plant and soil moisture relationships in a vineyard (vitis vinif era var. chenin blanc)
Van Zyl, J. L.; Weber, H. W.
In a field plot trial with grape vines planted on a high potential soil, the soil moisture status on different irrigation treatment plots was compared with that of a dryland control. Soil moisture budgeting was based on physical soil properties and root distribution patterns before treatments commenced. A maximum concentration of roots occurred at the 300-450 mm depth zone, while approximately 90 per cent of the total number of roots was found above 900 mm. Tensiometric readings of soil moisture potential, supplemented by electrometric resistance readings from gypsum blocks, indicated complete depletion between veraison and harvesting of the total available moisture on dryland plots. Despite this severe moisture stress as illustrated by chrono-isopletes, a reasonably good grape yield was still produced by the dryland vines, indicating either exceptional drought resistance or the uptake of water from extraneous sources. Supplementary irrigations greatly improved soil moisture conditions during the important growth stages of (a) flowering and fruit set, (b) green berry stage and (c) veraison. Moisture depletion patterns changed markedly as the season progressed from November to January, and as naturally stored rain water became depleted. In contrast to the absorption pattern in November, the fastest rate of water loss occurred in the deepest root zones during January, because of unsaturated moisture flow into the dry partly decomposed parent material. The apparently unproductive subsoil might act as a large natural reservoir for superfluous winter rain, which in summer becomes available to the vines through unsaturated upward flow into the root zone. Determination of leaf water potential showed unexpectedly high values at night (minima of -283kPa) in plants growing in soil of which the major part was dried below wilting point. Vines were thus able to regain turgidity at night. Crop factors for use with the American Class A-pan for scheduling irrigations were calculated. Crop factors were low (November to February = 0,20-0,30), and again emphasised the ability of vines to use water frugally. Crop factors were strongly dependent upon soil moisture conditions. Empirical coefficients for use in the Blaney-Criddle formula are also presented.
CITATION: Van Zyl, J. L. & Weber, H. W. 1981. The effect of various supplementary irrigation treatments on plant and soil moisture relationships in a vineyard (vitis vinif era var. chenin blanc). South African Journal of Enology & Viticulture, 2(2):83-99, doi:10.21548/2-2-2400.; The original publication is available at http://www.journals.ac.za/index.php/sajev
1981-01-01T00:00:00ZThe possible cause of red leaf disease and its effect on barlinka table grapeshttp://scholar.sun.ac.za:80/handle/10019.1/101746
The possible cause of red leaf disease and its effect on barlinka table grapes
Saayman, D.; Lambrechts, J. J. N.
The so-called red leaf (RL) phenomenon of Barlinka table grapes was investigated in the Hex River Valley, De Doorns. The symptoms of RL were found to resemble those of grapevine leafroll (GLR) disease to a certain extent, but also differed markedly from GLR in that initial reddening occurs in veins of apical leaves, with the typical downward curling of affected leaves not a distinctive feature. Like GLR, RL induces uneven and retarded ripening, small and shot berries, without colour in extreme cases, making the grapes worthless for export. Vine vigour is also seriously reduced. The cause of RL was found not to be a Ca deficiency as previously postulated and generally accepted. Foliar and soil applied Ca proved ineffective. Reciprocal grafting of red leaf-affected and heat-treated plant material showed that RL is associated with plant-transmissible pathogens, probably similar or belonging to viruses associated with GLR.
CITATION: Saayman, D. & Lambrechts, J. J. N. 1993. The possible cause of red leaf disease and its effect on barlinka table grapes. South African Journal of Enology & Viticulture, 14(2):26-32, doi:10.21548/14-2-2173.; The original publication is available at http://www.journals.ac.za/index.php/sajev
1993-01-01T00:00:00ZNitrogen mineralisation in vineyard soils of the Western Cape as affected by soil management practiceshttp://scholar.sun.ac.za:80/handle/10019.1/101735
Nitrogen mineralisation in vineyard soils of the Western Cape as affected by soil management practices
Raath, P. J.; Saayman, D.
Soil management practices like ridging, liming and irrigation are expected to affect the ability of microorganisms to mineralise plant residues in the soil through their effects on water regime, temperature, pH, organic C and total N contents. Investigations into seasonal changes in the mineral N contents of typical vineyard soils, as affected by these practices, were initiated during 1991 in existing vineyard trials. Soil water, soil temperature and mineral N were measured at regular intervals over two growing seasons. Ridged soil showed higher N release than non-ridged soil during winter, resulting in higher mineral N content at budburst. The effect of liming on microbial activity probably abated after 5 years because no difference in mineral N contents were obtained between soils of different pH. Irrigation showed no effect on N release, probably because of treatment design. Decreases in mineral N content during the growing season in soils from all the trials could not always be attributed to uptake by grapevines or to decreases in potentially mineralisable N contents and microbial activity.
CITATION: Raath, P. J. & Saayman, D. 1995. Nitrogen mineralisation in vineyard soils of the Western Cape as affected by soil management practices. South African Journal of Enology & Viticulture, 16(1):7-13, doi:10.21548/16-1-2263.; The original publication is available at http://www.journals.ac.za/index.php/sajev
1995-01-01T00:00:00ZThe effect of fertilisation on the performance of Barlinka table grapes on sandy soil, Hex River Valleyhttp://scholar.sun.ac.za:80/handle/10019.1/101732
The effect of fertilisation on the performance of Barlinka table grapes on sandy soil, Hex River Valley
Saayman, D.; Lambrechts, J. J. N.
The response of Barlinka table grapes on grayish, sandy soil to irrigation-applied N fertilisation levels, patterns of N application, crop load and stock P and K fertilisation, were evaluated over a 12-year period in the Hex River Valley. Under the conditions of the trial, an N level of about 100 kg ha-1 appeared to be optimum for shoot growth and grape quality. Bunch and crop mass benefited from increased N levels, apparently due to better berry set. Increased N levels also appeared to preserve greenness of bunch stems better during cold storage but N levels higher than 105-120 kg ha-' reduced colour and sugar content of berries. Applying 67% of total seasonal N during the pre-bloom to veraison period and the rest after harvest, as against a 50:50 distribution, had a slight, positive effect on shoot growth and bunch size, again apparently caused by better berry set. Indications of a small, positive response of shoot growth to stock P fertilisation were obtained. Potassium applied in this manner was found to be ineffective due to leaching and regular irrigation-applied K fertilisation had to be adopted. Increased crop load had a marked negative effect on shoot growth and grape quality, in the latter case comparable in magnitude to that of too high N levels. A balanced crop load of 22 bunches per vine with a shoot mass of 1,822 kg, was calculated for this trial, but a crop load of 18-19 bunches per vine appeared to be the maximum that still ensured the best quality.
CITATION: Saayman, D. & Lambrechts, J. J. N. 1995. The effect of fertilisation on the performance of barlinka table grapes on sandy soil, Hex River Valley. South African Journal of Enology & Viticulture, 16(2):41-49, doi:10.21548/16-2-2273.; The original publication is available at http://www.journals.ac.za/index.php/sajev
1995-01-01T00:00:00ZThe effect of irrigation system and crop load on the vigour of Barlinka table grapes on a sandy soil, Hex River Valleyhttp://scholar.sun.ac.za:80/handle/10019.1/101731
The effect of irrigation system and crop load on the vigour of Barlinka table grapes on a sandy soil, Hex River Valley
Saayman, D.; Lambrechts, J. J. N.
The effect of drip and micro-sprinkler irrigation, as well as crop load, on the vigour of Barlinka table grapes was studied in a field trial in the Hex River Valley over a 12-year period. Regulating soil water by means of tensiometers alone proved to be ineffective in the case of drippers, causing reduced vigour compared to micro-sprinklers. This could be rectified by using a fixed 2-day schedule and evaporation data. Increased bunch numbers per vine were found to have a pronounced and consistently depressive effect on shoot mass. It was proposed that an approach be followed of deciding on an acceptable vigour and then allocating bunches accordingly, using a formula developed from data obtained in this experiment. Significant seasonal variation in vigour caused by crop load and indications of similar effects due to calculated water deficits, were obtained. Combining these two factors in a regression model, shoot mass data were recalculated, revealing no consistent effect of irrigation systems on shoot growth. Mean seasonal water requirements were found to be 569 mm for micro-sprinklers and 411 mm for drippers. The more than 25% saving with drippers was mainly due to a reduced wetted soil volume.
CITATION: Saayman, D. & Lambrechts, J. J. N. 1995. The effect of irrigation system and crop load on the vigour of barlinka table grapes on a sandy soil, Hex River Valley. South African Journal of Enology & Viticulture, 16(2):26-34, doi:10.21548/16-2-2269.; The original publication is available at http://www.journals.ac.za/index.php/sajev
1995-01-01T00:00:00ZThe effect of residue management on the nutrient cycle in the production of rooibos (Aspalathus linearis) at Nieuwoudtville, Northern Capehttp://scholar.sun.ac.za:80/handle/10019.1/101329
The effect of residue management on the nutrient cycle in the production of rooibos (Aspalathus linearis) at Nieuwoudtville, Northern Cape
Nieuwoudt, Stephanus Francois
ENGLISH ABSTRACT: Rooibos (Aspalathus linearis) is a sensitive fynbos species with a large genetic variation, adapted to acid, nutrient poor soils, and can only be grown in certain parts of the Western- and Northern-Cape. Rooibos yields are getting poorer with increasing age of the field and the lifespan of rooibos are also just a maximum of 5 years commercially produced. A lot of medicinal/health research has been done and published on rooibos, but not much on the agricultural production aspects of rooibos. In order to increase the production and lifespan of rooibos tea further research needs to be done to better understand the rooibos plant in its cultivated environment. The role of leaf litter in fynbos, particularly in the cultivated rooibos nutrient cycle is still a grey area that could open up key management principles regarding plant water availability and plant nutrition style. The hypothesis is that the method of harvesting the rooibos seed by removing the litter layer without returning it under the plant can have a negative impact on the nutrient pools and cycle and thus lead to a shorter lifespan. The main aim was thus to look at the effect of different residue treatments on the rooibos plant nutrient cycle (uptake and nutrient pools).
Four sites across the Nieuwoudtville Bokkeveld region were selected with all the rooibos plants being ± 2 years old. Four different mulch treatments; a bare soil (leaf residue removed) treatment imitating seed harvesting (A), an added rooibos mulch (B), a natural leaf mulch (C) and an enriched rooibos mulch (D) were prepared at 4 sites. The chemical properties of soil and plant tissue from rooibos plants were tested. 5TE soil probes were used to measure the volumetric water content, EC and temperature at two soil depths of each treatment. All measurements were also duplicated using near-infrared spectroscopy (NIRS), to generate a database for future reference and to build calibrations that will be able to predict the nutrient content in the soils and plants.
It was found that soil chemical properties including P (mg kg-1), Na (cmolc kg-1), K (cmolc kg-1), Ca (cmolc kg-1), Mg (cmolc kg-1), Zn (mg kg-1), Mn (mg kg-1), C (%) and % Na (at pH 7); and plant chemical properties including Na (%) and plant N (%), P (%), K (%), Al (mg kg-1) and Fe (mg kg-1) all had a significant effect of the regrowth models using multiple regression analysis. Soil P, Mg and K had the biggest positive influences on the regrowth models. During this process it was found that the N:P ratio in soil plays an important role in the uptake of N and growth. Only at treatment D, with the lowest soil N:P ratio, plant N (%) had a positive influence on the regrowth multiple regression model. Plant N and P had a moderate positive correlation (R2=0.56).
Nutrient uptake by the rooibos plant was very high from July 2015 to September 2015. These nutrients included N, P, K, Ca, Mg, Zn, Mn, Fe and Al. From September 2015 to January 2016 however the uptake was lower for all the nutrients, but for K and Mg the uptake was higher compared to the other nutrients. The decrease in plant nutrient concentration from September 2015 to January 2016 is a result of less nutrient uptake and nutrient dilution following rapid growth of plant. There was an increase in soil exchangeable Mg and Ca from July 2015 to September 2015 due to increase in soil pH during this time. Soil exchangeable Ca (R2=0.49) and Mg (R2=0.61) correlated positively with pH, thus the increase in soil exchangeable Ca and Mg can be due to the increase in pH. For all the treatments there was a total decrease in soil N (significant for A and B) and plant N over the one-year period. The plant Al and Zn for all the treatments also increased over the one-year period. The increase in plant Al was not significant and the increase in plant Zn was significant for all treatments. From July 2015 to January 2016 there were differences in growth between the treatments. Treatment A resulted in the lowest estimated dry matter increase during this period and for treatment B it was the highest. The difference in estimated dry matter increase between these two treatments was also statistically significant. The estimated dry matter increase for treatment C and D was higher than treatment A but it was not significant. The mulch treatments, especially treatment B, resulted in higher P, K and Mg uptake. For all the treatments, except treatment D, the soil P decreased over the one-year period. For treatment B and D the plant P increased significantly compared to treatment A and C where the increase was not significant. The mulch treatments showed an increase in plant K, but it was only significant for treatment B over the one-year period. For all the treatments there was an increase in plant Mg, but only for treatment A the increase was not significant. All the mulch treatments also conserved more water for longer compared to treatment A. The combination of nutrient leaching from the mulch (Mg and K) and the conservation of more soil water may be the reason for the higher nutrient uptake by treatment B and thus the better growth.
From the NIRS study it was found that for these sandy soils it was only exchangeable Mg that could be predicted with good accuracy (RPD>2). The soil chemical properties pH, H (cmolc kg-1), K (mg kg-1), Ca (cmolc kg-1), Fe (mg kg-1) and C (%) models showed satisfactory predictability. For plant samples NIRS predicted P (%) and Mg (%) with good accuracy. The prediction models for N (%), K (%), Ca (%) and Na (mg kg-1) were only satisfactory and for the rest it was unreliable. From these results it was thus not possible to quantitatively predict all the chemical properties in the soil and plant samples but there is potential for better calibrations in the future.
Differences in growth and vigour can also be attributed to location. The micro conditions in which a single plant grows, related to the impact of normal agricultural practices, was found to also determine the success of rooibos production. The hypothesis was supported by treatment C (the plant where natural mulch was not removed) having a higher estimated dry matter increase compared to treatment A (bare soil), but this difference was not significant. Treatment B (added mulch) however showed to have a significant impact. Rooibos production systems are far from being optimized and the amounts of unknown impacts were narrowed down by this work. This research indicates that the rooibos plant is genetically unrefined and that agricultural practices should focus more towards the natural state of fynbos nutrient availability and growth.; AFRIKAANSE OPSOMMING: Rooibos (Aspalathus linearis) is ŉ sensitiewe fynbos spesie met groot genetiese variasie, aangepas vir suur, voedingstof arme gronde en kan net verbou word in sekere gedeeltes van die Wes- en Noord-Kaap. Rooibos opbrengste raak al hoe swakker met toenemende ouderdom van die veld en die lewensduur van rooibos is ook net ŉ maksimum van 5 jaar (kommersieel verbou). Baie medisinale en gesondheidsnavorsing is al gedoen en gepubliseer, maar min op die landbouproduksie aspek van rooibos. Om die produksie en lewensduur van rooibostee te verhoog en te verleng word verdere navorsing benodig om die rooibos plant in sy kommersieel verboude omgewing beter te verstaan. Die rol van ŉ blaar deklaag in fynbos, veral in die rooibos voedingstof siklus, is nog steeds ŉ onbekende area en kan lei tot baie belangrike bestuurs praktyke , met betrekking tot plant water beskikbaarheid en plantvoeding styl. Die hipotese is dat die manier waarop die rooibos saad geoes word deur die verwydering van die natuurlike blaar deklaag sonder om dit terug te sit onder die plant ŉ negatiewe impak op die voedingstof poele en siklus het en dus lei tot laer opbrengste en ŉ korter rooibos lewensduur. Die hoofdoel van die studie was dus om te kyk na die effek van verskillende rooibos blaar deklae op die rooibos plantvoedingstof siklus (opname en voedingstof poele).
Vier eksperimentele areas (± 2 jaar oud rooibostee) oor die Nieuwoudtville Bokkeveld Plato streek is gekies waar die proewe uitgevoer sou word. Vier verskillende deklaag behandelings; ŉ kaal grond (A) (nabootsing van waar saad verwyder is), ŉ ekstra rooibos blaar deklaag (B), ŉ natuurlike blaar deklaag (C) en ŉ verrykte rooibos blaar deklaag (D) is voorberei by elkeen van die uitgesoekte areas. Die chemiese eienskappe (voedingstof status) van die grond en rooibos plantweefsel is ontleed. 5TE grond sensore is gebruik om die volumetriese waterinhoud, temperatuur en EC te meet op twee dieptes, een plant van elke behandeling. Al die grond en plant monster ontledings is ook gedupliseer met behulp van NIR spektroskopie om ŉ databasis vir toekomstige verwysing te genereer en om kalibrasies, wat ons in staat sal stel om die voedingstofinhoud in die grond en plante te kan voorspel.
Deur gebruikmaking van veelvuldige regressie ontledings is dit bevind dat die grond chemie, [P (mg kg-1), Na (cmolc kg-1), K (cmolc kg-1), Ca (cmolc kg-1), Mg (cmolc kg-1), Zn (mg kg-1), Mn (mg kg-1), C (%) en % Na (by pH 7)] en plant chemiese eienskappe [Na (%) en plant N (%), P (%), K (%), Al (mg kg-1) en Fe (mg kg-1)] almal ŉ beduidende effek gehad het op die hergroei modelle. Deur hierdie proses van uitkenning t.o.v. die belangrikste voedingstowwe, is bevind dat die N:P verhouding in die grond ŉ belangrike rol speel met die opname van N en ook groei. Net by behandeling D, met die laagste N:P verhouding, het plant N (%) ŉ positiewe effek gehad in die hergroei model. Plant N en P het ŉ positiewe korrelasie getoon (R2=0.56).
Voedingstof opname deur die rooibos plante was baie hoog vanaf Julie 2015 tot September 2015. Hierdie voedingstowwe sluit in N, P, K, Ca, Mg, Zn, Mn, Fe en Al. Van September 2015 na Januarie 2016 was dit laer vir al die voedingstowwe, maar vir K en Mg was die opname hoër in vergelyking met die ander voedingstowwe. Die afname in plant voedingstof konsentrasie vanaf September 2015 na Januarie 2016, is ŉ gevolg van minder voedingstof opname en verdunning a.g.v. die drastiese toename in groei. Daar was ŉ toename in grond uitruilbare Mg en Ca van Julie 2015 na September 2015 a.g.v. die toename in grond pH. Grond uitruilbare Ca (R2=0.49) en Mg (R2=0.61) het positief gekorreleer met grond pH, dus die gevolglike toename in uitruilbare Ca en Mg met toename in pH. Vir al die behandelings is daar 'n totale afname in die grond N bespeur (belangrik vir A en B) en plant N oor die tydperk van een jaar. Die plant Al en Zn vir al die behandelings het ook toegeneem oor die tydperk van een jaar. Die toename in die plant Al was nie betekenisvol nie, maar die toename in die plant Zn was betekenisvol vir alle behandelings. Vanaf Julie 2015 tot Januarie 2016 was daar verskille in groei tussen die behandelings. Behandeling A het die laagste beraamde toename in droëmassa getoon gedurende hierdie tydperk, en vir behandeling B was dit die hoogste. Die verskil in beraamde droëmassa toename tussen hierdie twee behandelings was statisties betekenisvol. Die beraamde droëmassa toename vir behandeling C en D was hoër as behandeling A, maar was nie statisties betekenisvol nie. Die deklaag behandelings, veral behandeling B, het gelei tot hoër P, K en Mg opname. Vir al die behandelings, behalwe behandeling D, het die grond P afgeneem oor die tydperk van een jaar. Vir behandeling B en D het die plant P aansienlik toegeneem in vergelyking met behandeling A en C. Slegs die deklaag behandelings het 'n toename in die plant K getoon, maar net vir behandeling B oor die tydperk van een jaar was die toename betekenisvol. Vir al die behandelings was daar 'n toename in die plant Mg, maar slegs vir behandeling A was die toename nie betekenisvol nie. Al die deklaag behandelings het ook meer water vir langer bewaar in vergelyking met behandeling A. Die kombinasie van voedingstof loging uit die deklaag (Mg en K) en die bewaring van meer grondwater m.b.v. van deklae, kan die rede wees vir die hoër voedingstof opname veral deur behandeling B en dus beter groei.
Vanuit die NIRS studie was bevind dat, vir die baie sanderige gronde, dit net uitruilbare Mg (cmolc kg-1) was wat voorspel kon word met hoë akkuraatheid (RPD>2). Die modelle vir die grond chemiese eieskappe [pH, H (cmolc kg-1), K (mg kg-1), Ca (cmolc kg-1), Fe (mg kg-1) en C (%)] het bevredigende voorspelbaarheid vertoon. By die plantmonsters was dit net die P (%) en Mg (%) wat met hoë akkuraatheid voorspel kon word. Die modelle vir N (%), K (%), Ca (%) en Na (mg kg-1) was net bevredigend en vir die res onbetroubaar. Van hierdie resultate was dit dus nie moontlik om al die chemiese eienskappe van die grond en plant monsters kwantitatief akkuraat te voorspel m.b.v. NIRS nie, maar daar is potensiaal met verdere navorsing vir 'n beter kalibrasies in die toekoms.
Verskille in groeikrag kan ook toegeskryf word aan spesifieke ligging. Met die mikro omstandighede waarin ŉ enkele plant groei, wat verband hou met die impak van normale landboupraktyke, is bevind dat dit ook die sukses van rooibos produksie bepaal. Die hipotese is ondersteun deur behandeling C (die plant waar natuurlike deklaag nie verwyder) wat 'n hoër geraamde droëmateriaal toename in vergelyking met behandeling A (kaal grond) getoon het, maar die verskil was nie betekenisvol nie. Behandeling B (bygevoegde deklaag) het egter tot 'n betekenisvolle toename in groei getoon. Rooibos produksiestelsels is vêr van optimaal en die hoeveelheid van onbekende impakte is verklein deur hierdie werk. Hierdie navorsing dui daarop dat die rooibos plant geneties onverfynd is en dat landboupraktyke meer moet fokus op die natuurlike toestand van fynbos voedingstof beskikbaarheid en groei.
Thesis (MScAgric)--Stellenbosch University, 2017.
2017-03-01T00:00:00ZAn evaluation of lime Requirement methods for selected South African soilshttp://scholar.sun.ac.za:80/handle/10019.1/101100
An evaluation of lime Requirement methods for selected South African soils
Van der Berg, Vincent
ENGLISH ABSTRACT: A laboratory study was conducted to evaluate seven widely used methods to predict soil lime
requirement (LR) using 20 acidic South African top and sub-soils with a wide range of properties. The
LR methods which were evaluated against a standard CaCO3 incubation LR procedure, included: the
original Eksteen method with organic matter correction factor (OMCF) , commonly used in the Western
Cape; two modifications of the Eksteen method, namely: (i) Eksteen-KCl method, involving the use of
1 M KCl exchangeable acidity instead of titratable acidity at pH 7, and (ii) Modified-Eksteen method,
where a correction factor was applied to titratable acidity that was derived from soil data obtained in
this study; the Cedara method, most commonly used in KwaZulu-Natal; the ARC-SGI method,
developed primarily for Free State soils by the ARC- Small Grain Institute in Bethlehem; the
Shoemaker-McLean-Pratt single buffer (SMP-SB) method most commonly used in the North East and
North Central regions of the USA; the Adams and Evans single buffer (AE-SB) method most commonly
used in the South East and Mid-Atlantic regions of the USA.
The original Eksteen method, although highly correlated with incubation LR, was found to be a
relatively inaccurate predictor of LR. The Eksteen-KCl and Cedara methods were found to be highly
correlated with incubation LR, yet consistently underestimated LR. The modified-Eksteen method was
found to be highly correlated with incubation LR, and was a good predictor of LR. The ARC-SGI
method was a considerably poorer predictor of LR, and tended to grossly overestimate LR. The SMPSB
method was found to be highly correlated with incubation LR, and was shown to be reasonably
accurate to achieve a target pHKCl of 5.5. Recalibration of the SMP-SB soil-buffer pH with incubation
LR resulted in considerable increases in accuracy. The AE-SB method was found to be highly
correlated with incubation LR, yet tended to overestimate LR. Recalibration of the AE-SB soil-buffer
pH with incubation LR resulted in a sufficient increase in accuracy.
A correlation study was conducted to investigate the relationship between soil properties and both
incubation LR and LR methods. It was revealed that soil properties other than soil pH, which are useful
indicators of LR are: soil C > variable charge > CECpH 7 > clay + silt. Soil C was found to be a significant
contributor to LR due to its association with exchangeable Al and due to its high pH dependent acidity.
Titratable acidity was found to be the soil property that most strongly related to soil LR. Variable
charge was also shown to exhibit significant relationships with soil parameters that most strongly
influence LR. For these reasons, a multiple regression equation was developed that utilised only
titratable acidity and variable charge. The multiple regression equation was able to predict 96.76% of
the variation observed for incubation LR, and was 97.86% accurate in predicting the LR for each
specific soil to obtain a target pHKCl of 5.5. Regarding the relationship between soil properties and LR
methods, it was revealed that the local methods, except the ARC-SGI method, were most strongly
influenced by exchangeable acidity and Al, and had significant relationships with soil C. The American direct buffer methods were strongly correlated with essentially all of the soil properties studied. This
is indicative of the ability of these methods to directly determine the amount of acidity that may
originate from various sources in the soil, in order to make a sufficiently accurate LR. It is therefore
recommended that the application of direct buffer methods be further developed for use on South
African soils in order to further improve the accuracy of LR determination in South Africa. The existing
method that was found to most accurately predict LR on a wide range of soils was the modified-Eksteen
method.; AFRIKAANSE OPSOMMING: ŉ Laboratorium studie was uitgevoer om sewe metodes te evalueer, wat algemeen gebruik word om
kalkbehoefte (KB) te bepaal, op 20 suur Suid-Afrikaanse bo- en ondergronde wat oor ŉ wye reeks
eienskappe beskik. Die KB metodes wat geëvalueer was, teenoor ŉ standaard CaCO3 inkubasie KB
prosedure, was: die Eksteen metode met organiese materiaal korreksie faktor (OMKF) wat algemeen in
die Wes-Kaap gebruik word; ingesluit was twee veranderinge tot die oorspronklike metode, naamlik:
(i) die Eksteen-KCl metode, wat die gebruik van 1 M KCl uitruilbare suur bewerkstellig, i.p.v.
titreerbare suur by pH 7, en (ii) die gemodifiseerde Eksteen metode, waartoe ŉ korreksie tot die
titreerbare suur data toegepas is soos verkry in die studie; die Cedara metode, wat algemeen in KwaZulu
Natal gebruik word; die ARC-SGI metode, wat primêr vir Vrystaatse gronde ontwikkel is deur die LNR
Klein Graan Instituut in Bethlehem; die Shoemaker-McLean-Pratt enkel buffer (SMP-SB) metode, wat
algemeen in die Noord-Oostelike en sentrale Noordelike streke van die V.S.A gebruik word; die Adams
en Evans enkel buffer (AE-SB) metode, wat algemeen in die Suid-Oostelike en mid-Atlantiese streke
van die V.S.A. gebruik word.
Dit was gevind dat die oorspronklike Eksteen metode ŉ relatiewe onakkurate voorspeller vir KBbepaling
was, alhoewel ŉ sterk verwantskap gevind was tussen dié metode en die inkubasie KB metode.
Die Eksteen-KCl en Cedara metodes het sterk gekorreleer met die inkubasie KB, maar het in meeste
gevalle die KB om ŉ teiken pH te bereik onderskat. Die gemodifiseerde Eksteen metode het ŉ sterk
verwantskap met die inkubasie KB getoon, en was oor die algemeen ŉ goeie voorspeller van KB om ŉ
teiken pH te bereik. Die ARC-SGI metode was veral ŉ hoogs onakkurate voorspeller van KB, en het
daartoe geneig om KB drasties te oorskat. Die SMP-SB metode het ŉ sterk verwantskap met die
inkubasie KB getoon, en was gevind om bevredigend akkuraat te wees in die geval van KB bepaling
om ŉ teiken pH te bereik. Kalibrasie van die SMP-SB grond-buffer pH met inkubasie KB het ŉ toename
in akkuraatheid tot gevolg gehad. Die AE-SB metode het ŉ sterk verwantskap met die inkubasie KB
getoon, maar het daartoe geneig om KB te oorskat. Kalibrasie van die AE-SB grond-buffer pH met
inkubasie KB het egter ŉ bevredigende toename in akkuraatheid tot gevolg gehad.
ŉ Korrelasie studie was uitgevoer om die verhouding tussen grondeienskappe en beide inkubasie en KB
metodes te ondersoek. Dit was bevind dat grondeienskappe anders as grond pH wat KB bepaal die
volgende insluit: grond C > veranderlike lading > KUKpH 7 > klei + slik. Dit was bevind dat grond C
die grootste bydrae tot KB gehad het, a.g.v. C se assosiasie met uitruilbare Al en die groot bydrae
daarvan tot pH veranderlike suurheid. Titreerbare suur was bevind om die grondeienskap te wees wat
die sterkste verwantskap met KB het. Veranderlike lading het ook sterk verhoudings met
grondeienskappe wat KB sterk beïnvloed getoon. Vir hierdie redes was ŉ veelvoudige regressie
formule ontwikkel wat slegs titreerbare suurheid en veranderlike lading in ag neem. Die veelvoudige regressie model was in staat daartoe om 96.76% van die variasie te beskryf om ŉ KB te bepaal vir ŉ
spesifieke grond om ŉ teiken pHKCl van 5.5 te bereik. Rakende die verhouding tussen grondeienskappe
en KB metodes, was dit bevind dat plaaslike metodes – behalwe die ARC-SGI metode – die meeste
deur uitruilbare suur, Al en C beïnvloed was. Die Amerikaanse direkte buffer metodes het sterk
verwantskappe met feitlik alle geëvalueerde grondeienskappe getoon. Hierdie bevindinge toon dat die
bestudeerde direkte KB metodes daartoe in staat is om alle suurheidsbronne in ag te neem tydens die
voorspelling van KB. Dit word daarom aanbeveel dat die toepassing van sogenaamde direkte buffer
metodes verder ontwikkel word vir gebruik op Suid-Afrikaanse gronde, om sodoende die akkuraatheid
van KB bepalings te verhoog. Die bestaande metode wat bevind was om oor die algemeen die meeste
akkuraat te wees op ŉ wye reeks gronde, was die gemodifiseerde Eksteen metode.
Thesis (MSc)--Stellenbosch University, 2017.
2017-03-01T00:00:00ZLong-term effect of tillage and crop rotation practices on soil C and N in the Swartland, Western Cape, South Africahttp://scholar.sun.ac.za:80/handle/10019.1/101256
Long-term effect of tillage and crop rotation practices on soil C and N in the Swartland, Western Cape, South Africa
Cooper, Glen David
ENGLISH ABSTRACT: Soil Organic Matter (SOM) is an important indicator of soil quality influencing nutrient availability, water infiltration and retention and soil biological activity. The loss of SOM due to intensive cultivation is a growing concern worldwide. The Swartland is an important small grain production region in South Africa. It is situated in a semi-arid Mediterranean climate and as such has low SOM content (0.75 - 1.5 %). Conservation agriculture is the implementation of reduced tillage and diverse crop rotations and is seen as a possible solution to declining SOM in agricultural soils. The purpose of this study is to observe the effect of three commonly practiced tillage treatments and five different crop rotations on soil C and N stocks in the soil and the two major soil organic matter functional pools, namely, Mineral bound (MB) and Particulate Organic Matter (POM).
The study was conducted on two long term trials on the Langgewens Research Farm, situated near Moorreesberg, Western Cape, South Africa (33°16’34.41” S, 18°45’51.28” E). The climate is semi-arid Mediterranean with an average rainfall of between 275-400 mm with 80% falling in the winter months (April – August). The soils in this region are mainly derived from Malmesbury shale and tend to be shallow and stony. The first trial site (Site A) was a long term tillage study in its 8th year and consisted of three different 4-year crop rotation systems each under three different tillage practices. The three crop rotations included two 100 % crop treatments: Wheat monoculture (WWWW); Wheat-Canola-Wheat-Lupin (WCWL); and one 50 % crop-50 % pasture treatment: Wheat-Medic-Wheat-Medic (WMWM). These treatments were planted under three tillage treatments: No tillage (NT); Minimum tillage (MT); Conventional tillage (CT). The second trial site (Site B) was a long term soil quality trial in its 19th year and consisted of four 4-year crop rotation systems under no tillage conditions. The four crop rotation systems included one 100 % crop system: Wheat monoculture (WWWW); and three 50 % crop-50 % pasture systems: Wheat-Medic-Wheat-Medic (WMWM); Wheat-Medic/Clover-Wheat-Medic/Clover (WMc); Wheat-Medic/Clover-Wheat-Medic/Clover with supplementary grazing on Salt Bush (WMc SB).
No tillage had the highest total C stocks (0-40 cm) under both WWWW and WMWM, 31 Mg C ha-1 and 30 Mg C ha-1. These were significantly greater than both the MT, 28 Mg C ha-1 and 27 Mg C ha-1 respectively, and CT, 22 Mg C ha-1 and 21 Mg C ha-1, treatments under the same respective crop rotations. The effect under WCWL differed in that MT (28 Mg C ha-1) preformed significantly better than both NT (22 Mg C ha-1) and CT (13 Mg C ha-1).
Conventional tillage under WCWL had the lowest total C stocks by a significant amount, 15 Mg C ha-1 lower than that of MT under the same crop. The two high biomass rotations, WWWW and WMWM have significantly greater total C stocks than that of WCWL. This is evident under both the CT (WWWW, 22 Mg C ha-1; WMWM 21 Mg C ha-1) and the NT (WWWWW 30 Mg C ha-1; WMWMW Mg C ha-1), where WCWL has a lower C stock of 13 22 Mg C ha-1 and 22 Mg C ha-1 respectively. WCWL however is able to accumulate a much higher total C stock under MT (28 Mg C ha-1), with there being no significant difference between it and WWWWW (28 Mg C ha-1) and WMWM (27 Mg C ha-1).
The majority (55-95 %) of soil C at all sites were found in the MB fraction, while POM contributes a significantly smaller percentage. Under all treatments we can observe the trend of POM-C contribution to total C decreases with depth. There was very little difference found between the MB-C of all tillage and crop rotation treatments. However, there was great variation in the POM-C content of the treatments. Under WMWM, CT had significantly greater POM-C than NT at the 10-20 cm profile, 5.80 g kg-1 and 4.92 g kg-1 respectively, likely due to deeper incorporation of surface residues under CT. Under WWWW, NT had significantly greater POM-C than CT in the 5-10 cm profile at 2.18 g kg-1 and 1.10 g kg-1, respectively. The effect of crop rotation was similarly undefined, there was little significant difference between treatments in the MB-C while the POM-C showed great variation. Under NT in the 5-10 cm profile, WCWL had the largest POM-C, 3.76 g kg-1, significantly greater than both WMWM with 2.91 g kg-1, and WWWW with 1.81 g kg-1. However at the 10-20 cm profile WWWW with 2.18 g kg-1, was significantly larger than both WMWM and WCWL, with 0.75 g kg-1 and 0.89 g kg-1 respectively.
Tillage was found to have the strongest influence on soil C stocks, with NT having the largest C stocks followed by MT, both being significantly greater than CT. Crop rotation had a lesser, but still significant influence on C stocks, but a larger role in N stocks. WWWW and WMWM had the greatest C stocks, while the reduced grazing on WMc SB also led to greater C stocks. The inclusion of a legume pasture (Medic and Medic-Clover) had a significant increase in N stocks while WCWL had the lowest N stock. The data gathered from this study, highlights the benefits of conservation agriculture through the usage of reduced tillage and high biomass producing leguminous pastures. WMWM and WMc SB under NT had excellent SOM accumulation and provide a diversified production system and would be recommended for this region for these reasons.; AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar
Thesis (MScAgric)--Stellenbosch University, 2017.
2017-03-01T00:00:00ZEffects of tillage practices on some key soil parameters : A case study in the Kwazulu-Natal Midlands, South Africahttp://scholar.sun.ac.za:80/handle/10019.1/101032
Effects of tillage practices on some key soil parameters : A case study in the Kwazulu-Natal Midlands, South Africa
Esmeraldo, Michael Quinten
ENGLISH ABSTRAT: Soil organic carbon in its different forms play an important role in the biological, chemical and physical quality of the soil and need to be better understood and managed to farm in a sustainable manner. Four different farming systems were evaluated in this study and the results were compared to grasslands that were used as a reference value. The four farming systems were: Conventional tillage maize, reduced tillage maize without legume rotation, reduced tillage maize with legume rotation and conservation agriculture maize (no-till). The experimental study site is situated in the Kwazulu Natal Midlands close to Greytown South Africa. Thirty five individual sites were sampled and studied; 8 conventional tillage sites, 7 reduced tillage without legume rotation sites, 5 reduced tillage with legume rotation sites, 9 conservation agriculture sites and 6 natural grasslands. Samples were taken in triplicate using 5 cm steel cores at depths of 2.5, 7.5, 12.5, 17.5, 30, 40, 50, 75 and 100 cm (unless restricted by rock) for bulk density and SOC determination, total microbial biomass, aggregate stability and other important soil parameters.
The objective of the study was to determine the influence of different long term tillage systems have on the soil organic carbon stocks and other soil parameters up to 1 m depth that are key to overall soil health. . The total Soil Organic Carbon (SOC) stocks declined in the following order CA (231,1 Mg/ha) > RT + legumes (217.3 Mg/ha) > CT (192.8 Mg/ha) > Grasslands (180.1 Mg/ha) > RT – legumes (177.5 Mg/ha). The reduced tillage without legume rotation treatment yielded the highest average C: N value over the 1 m depth, where the reduced tillage with legume rotation treatment yielded the lowest average from 5 cm – 20 cm depth. %. Significant differences in average soil porosity (α = 0.005) were found between CT and grasslands (P = 0.0357) as well as between RT with legume rotation and grasslands (P = 0.0175).
Conservation agriculture produced significantly higher Total Microbial Biomass (TMB) values as well as Water Stable Aggregates (WSA) compared to all the other farming systems including grasslands, with values ranging from 7.34 g/kg of soil in the top layer to 3.67 g/kg of soil at 50 cm for TMB. The results for TMB showed that there were significant differences (α = 0.05) between CA and CT (P = 0.0267) as well as between CA and grasslands (P = 0.0445). Water stable aggregates were clearly affected by tillage treatments according to these results. Strong significant differences (α = 0.05) were also found in the results between CA and CT (P = 0.0096), CA and grasslands (P = 0.0158) as well as between CA and RT (P = 0.0456).
These results show that practicing long term conservation agriculture approximates the soil carbon distribution pattern to a natural exponential decline function and improves some important soil parameters that play a key role in overall soil health and sustainability.; AFRKAANSE OPSOMMING: Geen opsomming beskikbaar
Thesis (MSc)--Stellenbosch University, 2017.
2017-03-01T00:00:00ZThe effect of composted biochar on compost properties and mineralisationhttp://scholar.sun.ac.za:80/handle/10019.1/100261
The effect of composted biochar on compost properties and mineralisation
Botha, Ockert Guillaume
ENGLISH ABSTRACT: Pyrolized carbon, also known as biochar, is a widely used soil conditioner recognized for its adsorption, C sequestration and agricultural qualities. This led to the investigation into the possible use thereof by small-scale sustainable farmers as a filter for agricultural olive or wine effluent, where after the spent biochar can be incorporated into composts to sterilize it from toxins and pathogens before being used as soil amendment. However, before these used biochar filters can be applied to compost, research is required to assess the affect that biochar could have on the composting process. This research project was therefore initiated to investigate the feasibility of adding biochar to composts, specifically focusing on the effect of type and amount of biochar on the composting process and mineralisation of the composts in soils. The final aim was to construct a method for quantifying biochar content in compost and soil that can be used to assess the stability of biochar in soils. Furthermore, none of this research has previously been done in South Africa or on two locally produced biochars.
The first experiment was constructed to evaluate the effect of two contrasting commercial biochars on composting; a relatively low-cost, crude, pine wood biochar produced using a low-tech slow pyrolysis technique at 450°C, and a significantly more expensive, refined eucalyptus biochar produced using a high-tech slow pyrolysis technique at 900°C. The biochars were applied at two application rates (10% and 20% dry weight) to a mixture of green and animal waste. The effect was measured through composting indices such as temperature, C/N ratio, pH and EC, and microbial activity. Results showed that the robust, low temperature pine biochar applied at 10% (d/w) is the most suitable for composting due to higher composting temperatures measured, lower C/N ratios in the final product and higher cumulative microbial activity relative to the other biochar treatments. However, all biochar and control composts were all classified as successfully matured and stabilized according to the indices used, indicating that both types of biochar and application rates can be used to produce compost.
The second experiment was aimed at comparing the carbon (C), nitrogen (N) and phosphorus (P) mineralisation of the composted biochar in relation to compost with biochar and biochar only under ideal laboratory conditions. The incorporation of these treatments into the soil showed that the composting process increased the composted biochars degradability with 7.6 – 11.7% more carbon dioxide (CO2) being respired than compost with biochar of the same quantity. Biochar type and quantity influenced the mineralisation as eucalyptus char in general, and all treatments containing 20% biochar proved to be least degradable by microbes. Nitrogen mineralisation results showed that regardless of biochar type, quantity or composting, all biochar containing treatments caused net N immobilization and reduced nitrification. Phosphorus availability was found to be improved for both biochars through composting and the addition of compost, especially for eucalyptus biochar of which the amount of available P surpassed that of pine biochar although pine biochar only applications released more P. A 6-month field trial experiment was also constructed to further evaluate the five composts’ C mineralisation under natural conditions. In this experiment there was found that all biochar containing compost produced 7.6 – 20.1% less CO2 than the control compost, of which eucalyptus biochar showed the least amount of respiration. Loss on ignition results also revealed that composted eucalyptus biochar was the least degradable composts as only 7.4% and 7.8% of the total SOM was lost. Density fractionation further illustrated that composted biochar remains in the soil in particulate form longer than conventional compost and is slower to transform into the mineral fraction. No discernable difference in biochar content within the composts could be seen after field application at 50 t/ha.
The final aim of developing a rapid and cost-effective quantification method with the use of near-infrared spectroscopy (NIRS), was completed by constructing a calibration range of soils and compost from both types of biochar. The spectra acquired was then used to create regression models that were used to predict biochar content in the final mature composts and field trial soils. The results showed that NIRS can be used to quantify biochar, to within the same order of magnitude, in both composts and soil mixtures, which is of great importance for C stock audits and assessing biochar decay over time.
Selecting the type of biochar for water filtration, composting and soil conditioning, would be dependent on the purpose of the application. Both biochars show the ability to be successfully composted and used as soil amendment with good C sequestration capabilities. However, pine biochar is more suitable for the composting process and sterilization as it results in higher temperatures and increased microbial activity. Eucalyptus biochar however, would be the best option for phosphorus mineralisation and building soil carbon stocks.; AFRIKAANS OPSOMMING: Biochar is ŉ grond verbeteringsmiddel wat wydbekend is vir adsorpsie, koolstof vaslegging en verskeie ander landboukundige gebruike. Hierdie eienskappe het na die ondersoek vir die moontlike gebruik daarvan deur kleinskaalse, boere gelei. Die doel is om dit as `n volhoubare filter vir olyf- of wynuitvloeisel te gebruik, waarna dit in kompos toegedien kan word om dit van gifstowwe en patogene te steriliseer. Voordat die gebruikte biochar filters egter toegevoeg kan word in komposhope, is navorsing nodig om te bepaal wat die invloed van biochar op die komposproses en komposkwaliteit sal wees. Hierdie navorsingsprojek was dus tot stand gebring om die haalbaarheid van gekomposteerde biochar te ondersoek met spesifieke fokus op die effek wat die tipe en hoeveelheid biochar op die afbreek en mineralisasie van die kompos in die grond sal hê. Die finale doel was ook om ŉ metode te skep vir die kwantifisering van biochar in kompos en grond sodat die stabiliteit van biochar beoordeel kan word.
Die eerste eksperiment was opgestel om die effek van twee kontrasterende, kommersiële biochars op kompos te evalueer. Die een biochar is relatief goedkoop, ru en geproduseer uit dennehout deur middel van stadige pirolise by 450°C, terwyl die ander een aansienlik duurder, meer verfynd en uit bloekomhout teen 900°C geproduseer is. Die biochars was in twee toedieningshoeveelhede (10% en 20% droë gewig) in 'n mengsel van groen materiaal en beesmis toegedien. Die effek van die biochar op die kompos is deur middel van verskeie kompos indekse soos temperatuur, C/N verhouding, pH, EG, en mikrobiese aktiwiteit gemeet. Resultate het getoon dat die ru, lae temperatuur dennehout biochar, toegedien teen 10% (D / w), die mees geskikte is vir kompos aangesien hoër kompos temperature gemeet is, laer C/N verhoudings in die finale produk was en hoër kumulatiewe mikrobiese aktiwiteit in vergelyking met die ander biocharbehandelings gevind is. Al die biochar-ryke komposhope was egter geklassifiseer as volledig gestabiliseer wat daarop dui dat beide tipes biochar en die toedieningshoeveelhede gebruik kan word om suksesvolle kompos te vervaardig.
Die tweede eksperiment was daarop gemik om die mineralisasie van koolstof (C), stikstof (N) en fosfor (P) onder ideale laboratoriumtoestande van die gekomposteerde biochar met kompos saam met biochar, en slegs biochar te vergelyk. Die toediening van hierdie behandelings in die grond het getoon dat gekomposteeerdebiochar tussen 7,6-11,7% meer koolstofdioksied (CO2) in vergelyking met kompos met dieselfde hoeveelheid biochar vrystel. Die hoeveelheid en tipe biochar het ook ‘n invloed gehad aangesien mineralisasie van bloekombiochar in die algemeen laer was, terwyl behandelings met 20% biochar die minste afbreekbaar was. Stikstof mineralisasie resultate het getoon dat, ongeag van die tipe of hoeveelheid biochar in die kompos, alle biochar-ryke behandelings netto immobilisasie van N veroorsaak. Fosforbeskikbaarheid het verbeter deur kompostering en die byvoeging van kompos, veral vir bloekomhoutbiochar waarvan die hoeveelheid beskikbare P dennehoutbiochar se hoeveelheid oortref het. ’n Ses maande veld-eksperiment is ook opgestel om koolstofmineralisasie van die vyf komposte onder natuurlike omstandighede verder te evalueer. In hierdie eksperiment is daar bevind dat alle gekomposteerde biochar behandelings 7,6-20,1% minder CO2 as die kompos beheerdes geproduseer het, waarvan bloekombiochar die minste gerespireer het. Verlies op ontstekingsresultate het ook getoon dat gekomposteerde bloekombiochar die minste afbreekbaar was aangesien net 7,4% en 7,8% van die totale OM verlore gegaan het. Digtheidsfraksionering het ook verder getoon dat gekomposteerde biochar langer in die grond bly as konvensionele kompos.
Die finale doel was om 'n vinnige en koste-effektiewe kwantifiseringsmetode te skep deur gebruik te maak van naby infrarooi spektroskopie (NIRS). Dit voeris uitgevoer deur 'n kalibrasie reeks te konstrueer met ‘n verskeidenheid van biochar hoeveelhede in beide grond en kompos. Die spektra wat verkry is, was daarna gebruik om ‘n regressiemodel te skep, wat dan gebruik was om biocharinhoud te voorspel in die finale kompos en veldgronde. Die resultate het getoon dat NIRS wel gebruik kan word om biochar te kwantifiseer binne dieselfde orde grootte in beide kompos en grondmengsels. Hierdie resultate is van groot belang vir koolstofvoorraad oudits en die beoordeling van biochar verval met verloop van tyd.
Die selektering van ŉ tipe biochar vir waterfiltrasie en kompos- en grondkondisionering is gevind om afhanklik te wees van die wyse van toediening. Beide biochar’s het die vermoë om suksesvol gekomposteer te word en as grondwysiging met 'n goeie K sekwestrasie vermoë gebruik te kan word. Dennebiochar blyk meer geskik te wees vir die komposterings proses in terme van sterilisasie, aangesien dit tot hoër temperature en verhoogde mikrobiese aktiwiteit lei. Bloekombiochar sou egter die beste opsie wees vir fosformineralisasie en die bou van grondkoolstof
Thesis (MScAgric)--Stellenbosch University, 2016.
2016-12-01T00:00:00ZInvestigating the suitability of land type information for hydrological modelling in the mountain regions of Hessequa, South Africahttp://scholar.sun.ac.za:80/handle/10019.1/100233
Investigating the suitability of land type information for hydrological modelling in the mountain regions of Hessequa, South Africa
Malan, Gert Jacobus
ENGLISH ABSTRACT: The Land Type database of South Africa combines soil associations with various terrain positions within a larger Land Type polygon. The Land Type structure provides the opportunity to unlock the terrain unit information through segmenting the larger Land Type polygon into terrain units. Geographical information systems have the capability to dissect the landscape into terrain morphological units, using remote sensing technology. There is a range of methods and software available that can be used to dissect the landscape, the challenge is to identify a method that would be compatible with Land Type terrain units.
The study area is the catchment of the Korentepoort dam, north of Riversdale in the Hessequa district of the Western Cape. The Hessequa region is regularly struck with drought which leads to an investigation into the water security of the region. The investigation includes the development of a hydrological model for the Korentepoort Dam and bordering catchments. Physically based hydrological models require detailed soil distribution maps with soil physical data. The physical characteristics are used to calculate the amount of surface runoff, drainage and streamflow. Hydrologists use the Land Type information to supply soil character for modelling purposes. The most common soil type from the Land Type memoir is selected to represent the whole Land Type polygon. This representation varies depending on the homogeneity of soils within the landscape, but can be as little as 20%.
The segmentation method is evaluated within the Korentepoort catchment by field observations of the terrain at 190 points in the landscape. This point data is compared to the segmentation map with a different range of acceptable error. The segmentation method is constructed on a 90-meter digital elevation model, which was refined to a 30 meter. The highest acceptable error was selected as 30 meters. At this error, the terrain map was able to predict 77% of the field observation points. Transects were created from the terrain map, which also indicates a good fit with terrain units.
The Land Type information in the catchment was found to be conflicting with field observations and thus updated. The updated Land Type information was used to populate the segmented terrain map. The high resolution of the terrain map was found to be too complex for the hydrological model. A well-used method of soil type aggregation on the basis of hydrology was applied to the updated Land Types. The method divides the soil types into three hydrological response units and was found to be accurate on 10 out of 13 selected profiles. These profiles are selected as modal profiles and represent the soil types of their respective terrain units.
This research made it possible to dissect the landscape into units comparable with those in the Land Type database. This increases the resolution of the Land Type information and could possibly be applied to the whole of South Africa. Methods are suggested in which these terrain maps can be aggregated in a meaningful manner which would enhance its applicability for hydrological modelling.; AFRIKAANS OPSOMMING: Die Land Tipe databasis van Suid Afrika groepeer grond tipes in assosiasies op verskillende terrein eenhede binne ŉ groter Land Tipe blok. Die Land Tipe inligting bied die geleentheid om hierdie terrein eenheid inligting te ontsluit deur die groter Land Tipe blok op te breek in verskillende terrein eenhede. Geografiese inligting stelsels het die potensiaal om deur middel van afstandswaarnemings tegnologie, ŉ landskap te verdeel in terrein morfologiese eenhede. Daar is wel ŉ verskeidenheid sagteware en metodes wat gebruik kan word om ŉ landskap te segmenteer, die uitdaging is om ŉ metode te identifiseer wat die landskap verdeel in eenhede wat ooreenstem met die in die Land Tipes.
Die studie area is die Korentepoort Dam opvangsgebied, noord van Riversdal in die Hessequa distrik van die Weskaap. Die Hessequa distrik word gereeld deur droogtes geraak wat daartoe gelei het dat ŉ ondersoek geloots is om die water sekuriteit van die gebied te ondersoek. Die ondersoek sluit in die ontwikkeling van ŉ hidrologiese model vir die Korentepoort Dam en nabye opvangsgebiede. Fisies gebaseerde hidrologiese modelle benodig gedetailleerde grond distribusie kaarte waaraan grond fisiese eienskappe gekoppel is. Hierdie fisiese eienskappe word gebruik deur die model om oppervlak afloop, dreinering en stroom vloei te bereken. Hidroloë maak gebruik van die Land Tipe databasis om grond inligting te bekom en dit in die model te gebruik. Die grond tipe wat die messte voorkom in ŉ Land Tipe blok word geselekteer om die hele blok te verteenwoordig. Die persentasie voorkoms kan varieer afhangende die homogeniteit van die gronde in die landskap, maar kan so laag as 20% wees.
Die segmentasie metode is geëvalueer binne die Korentepoort opvangsgebied deur terrein observasies te maak en dit te koppel aan punt data. Die punt data is vergelyk met die segmentasie kaart met inagneming van sekere faktore wat variasie kan veroorsaak. Die segmentasie metode is gebaseer op ŉ 90 meter digitale terrein model, wat verfyn is tot ŉ 30 meter. ŉ Aanvaarbare variasie van 30 meter is daarom geselekteer, waar die terrein kaart 77% van die observasie punte verteenwoordig het. Terrein deursneë is vergelyk met die terrein eenhede van die morfologie kaart wat visueel aanvaarbaar pas. Die Land Tipe inligting in die Korentepoort opvangsgebied het afgewyk van die veld waarnemings en is opgedateer. Die opgedateerde Land Tipe inligting is gebruik om die terrein morfologie kaarte te vul met grond inligting. Hierdie hoë resolusie kaart was te besig vir die hidrologiese model wat gelei het na samevoeging van sekere grond tipes. Hierdie samevoegings metode kombineer grond tipes teen opsigte van modale profiele wat die gronde beste voorstel. Die metode het samevoeging van blokke bewerkstellig en nogtans 10 uit 13 profiele in die opvangsgebied korrek verteenwoordig.
Die navorsing maak dit moontlik om die landskap in segmente in te deel wat vergelykbaar is met die Land Tipe terrein eenhede, wat die algehele resolusie van die Land Tipe inligting verbeter. Daarby is metodes voorgestel om hierdie inligting op ŉ sinvolle manier te groepeer wat dit ideaal maak vir hidrologiese modulering.
Thesis (MSc)--Stellenbosch University, 2016.
2016-12-01T00:00:00ZEffect of irrigation using diluted winery wastewater on vitis vinifera l. cv. cabernet sauvignon in a sandy alluvial soil in the Breede River Valley – vegetative growth, yield and wine qualityhttp://scholar.sun.ac.za:80/handle/10019.1/99905
Effect of irrigation using diluted winery wastewater on vitis vinifera l. cv. cabernet sauvignon in a sandy alluvial soil in the Breede River Valley – vegetative growth, yield and wine quality
Howell, C. L.; Myburgh, P. A.; Lategan, E. L.; Schoeman, C.; Hoffman, J. E.
The re-use of winery wastewater for irrigation was investigated in a field trial with micro-sprinklerirrigated
Cabernet Sauvignon/99Richter in the Breede River Valley region of South Africa. Irrigation
with winery wastewater diluted with river water to 100, 250, 500, 1 000, 1 500, 2 000, 2 500 and 3 000
mg/L chemical oxygen demand (COD) was compared to irrigation with river water. Under the prevailing
conditions, plant water status did not respond to irrigation using diluted winery wastewater. Leaf and
shoot element contents did not respond consistently to irrigation using diluted winery wastewater.
There were no differences in vegetative growth or yield or juice characteristics, with the exception of
juice pH. Consequently, water use and water status of the grapevines also were not affected. The results
indicate that a summer interception crop may increase the evapotranspiration of vineyards substantially.
The irrigation of grapevines using diluted winery wastewater did not have detrimental effects on wine
colour and sensory wine characteristics, and the grapevines did not respond to the COD level per se. This
indicates that sufficient aeration occurred between irrigations, which allowed organic carbon breakdown.
The low salinity and sodicity levels in the diluted winery wastewater could be a further explanation of why
the grapevines did not respond to the wastewater irrigation. In heavier soils, regions with lower winter
rainfall, situations where the winery wastewater contains more potassium or where no interception crop is
cultivated during summer, grapevine responses may be more pronounced.
Howell, C. L., et al. 2016. Effect of irrigation using diluted winery wastewater on vitis vinifera l. cv. cabernet sauvignon in a sandy alluvial soil in the Breede River CITATION: Valley – vegetative growth, yield and wine quality. active management of grapevine trunk disease pathogen infections in grapevine nurseries. South African Journal of Enology & Viticulture, 37(2):211-225, doi:10.21548/37-2-795.; The original publication is available at http://www.journals.ac.za/index.php/sajev
2016-09-01T00:00:00ZSpatial soil information in South Africa : situational analysis, limitations and challengeshttp://scholar.sun.ac.za:80/handle/10019.1/99398
Spatial soil information in South Africa : situational analysis, limitations and challenges
Paterson, Garry; Turner, Dave; Wiese, Liesl; Van Zijl, George; Clarke, Cathy; Van Tol, Johan
Soil information is vital for a range of purposes; however, soils vary greatly over short distances, making
accurate soil data difficult to obtain. Soil surveys were first carried out in the 1920s, and the first national soil
map was produced in 1940. Several regional studies were done in the 1960s, with the national Land Type
Survey completed in 2002. Subsequently, the transfer of soil data to digital format has allowed a wide range
of interpretations, but many data are still not freely available as they are held by a number of different bodies.
The need for soil data is rapidly expanding to a range of fields, including health, food security, hydrological
modelling and climate change. Fortunately, advances have been made in fields such as digital soil mapping,
which enables the soil surveyors to address the need. The South African Soil Science fraternity will have
to adapt to the changing environment in order to comply with the growing demands for data. At a recent
Soil Information Workshop, soil scientists from government, academia and industry met to concentrate
efforts in meeting the current and future soil data needs. The priorities identified included: interdisciplinary
collaboration; expansion of the current national soil database with advanced data acquisition, manipulation,
interpretation and countrywide dissemination facilities; and policy and human capital development in newly
emerging soil science and environmental fields. It is hoped that soil information can play a critical role in the
establishment of a national Natural Agricultural Information System.
CITATION: Paterson, G. et al. 2015. Spatial soil information in South Africa : situational analysis, limitations and challenges. South African Journal of Science, 111(5/6),
Art. #2014-0178, doi:10.17159/sajs.2015/20140178.; The original publication is available at http://sajs.co.za
2015-01-01T00:00:00ZEffect of irrigation with diluted winery wastewater on phosphorus in four differently textured soilshttp://scholar.sun.ac.za:80/handle/10019.1/99075
Effect of irrigation with diluted winery wastewater on phosphorus in four differently textured soils
Mulidzi, A. R.; Clarke, C. E.; Myburgh, P. A.
The wine industry needs solutions for wastewater treatment, as environmental legislation for its disposal is
increasingly being enforced due to non-compliance. The feasibility of re-using diluted winery wastewater
was assessed in a pot experiment under a rain shelter over four simulated irrigation seasons. Four soils
varying in parent material and clay content, viz. aeolic sand from Lutzville containing 0.4% clay, alluvial
sand from Rawsonville containing 3.3% clay, granite-derived soil from Stellenbosch containing 13% clay,
and shale-derived soil from Stellenbosch containing 20% clay, were irrigated with wastewater diluted to
3 000 mg/L COD (chemical oxygen demand), whereas the control received municipal water. Irrigation with
diluted winery wastewater increased the pH(KCl) in the shale- and granite-derived soils into the optimum
range for P availability. Although pH(KCl) in the aeolic sand was initially above the optimum range, relatively
high Na+ levels also caused available P to increase as the pH(KCl) increased. The pH(KCl) in the alluvial sand
increased beyond the optimum range, thereby causing a reduction in the available P. This indicates that
irrigation with diluted winery wastewater may only enhance P absorption if the pH(KCl) shift is towards the
optimum. It must be noted that the results represent a worst-case scenario, i.e. in the absence of rainfall
or crops.
CITATION: Mulidzi, A. R., Clarke, C. E. & Myburgh, P. A. 2016. Effect of irrigation with diluted winery wastewater on phosphorus in four differently textured soils. South African Journal for Enology and Viticulture, 37(1): 79-84, doi:10.21548/37-1-761.; The original publication is available at http://www.journals.ac.za/index.php/sajev
2016-04-01T00:00:00ZSeasonal variation in composition of winery wastewater in the Breede River Valley with respect to classical water quality parametershttp://scholar.sun.ac.za:80/handle/10019.1/99074
Seasonal variation in composition of winery wastewater in the Breede River Valley with respect to classical water quality parameters
Howell, C. L.; Myburgh, P. A.; Lategan, E. L.; Hoffman, J. E.
The annual wastewater quality dynamics of a winery from which wastewater was sourced for a field
experiment investigating the dilution of winery wastewater for vineyard irrigation were determined.
Annual mean monthly pH ranged from 4.2 to 6.8 and was lower during grape harvest than in winter.
Electrical conductivity (EC) increased from the start of harvest (February) and reached a maximum
in May, followed by a decline to a minimum in August. The increase in EC probably originated from
cleaning agents used in the winery, as well as K+ in the grape lees and spillage from the grape fermentation
process. With the exception of August, EC exceeded the critical value of 0.75 dS/m, which is the salinity
threshold for water used for grapevine irrigation. The mean monthly chemical oxygen demand (COD)
level increased from January and was highest at peak harvest (March). The K+ and Na+ levels in the winery
wastewater increased from February to May. The sodium adsorption ratio (SAR) ranged from 2.4 to 9.0
and increased from January to June. Although COD concentration in winery wastewater is the preferred
indicator of water quality for the South African wine industry, it did not provide a reliable indication of
suitability for irrigation. However, EC was strongly determined by the K+ concentration. This was to be
expected, since K+ is usually the most abundant cation in winery wastewater. Therefore, EC would be a
more reliable indicator of winery wastewater quality than COD concentration, particularly with regard to
the concentrations of cations such as K+ and Na+.
CITATION: Howell, C. L., et al. 2016. Seasonal variation in composition of winery wastewater in the Breede River Valley with respect to classical water quality parameters. South African Journal for Enology and Viticulture, 37(1): 31-38, doi:10.21548/37-1-756.; The original publication is available at http://www.journals.ac.za
2016-10-01T00:00:00ZThe effect of once-off tillage on selected soil physical and chemical properties and resultant crop response on a shale derived soil under no-till in the Swartland sub-region of the Western Capehttp://scholar.sun.ac.za:80/handle/10019.1/98833
The effect of once-off tillage on selected soil physical and chemical properties and resultant crop response on a shale derived soil under no-till in the Swartland sub-region of the Western Cape
Leygonie, Izane Riana
ENGLISH ABSTRACT: Conservation agriculture is widely adopted by farmers who claim that any soil disturbance will be detrimental to both soil physical and chemical properties. However, as the effect of reduced tillage and maximum stubble retention becomes more prevalent, secondary effects, positive or negative, may develop at soil surface or in the upper layers of the soil profile. Therefore, an increased interest in strategic tillage have arose in order to address the emerging CA constraints. CA can be defined as the avoidance of mechanical soil disturbance combined with the maintenance of a permanent soil cover and the implementation of a crop rotation system. The study formed part of a long-term field trial established in 2007 investigating different crop and crop/pasture systems under no-tillage at the Langgewens Research Farm of the Western Cape Department of Agriculture, near Moorreesburg, Swartland, Western Cape, South Africa. The study was conducted during the 2014 and 2015 growing seasons to assess the effect of once-off tillage (till once in 10 years) in long-term medic/wheat/medic/wheat (McWMcW), wheat/lupin/wheat/canola (WLWC), lupin/wheat/canola/wheat (LWCW), wheat/medic/wheat/medic (WMcWMc) and canola/wheat/lupin/wheat (CWLW) cropping systems (the last letter in the sequence represents the crop that was in field at sampling time). Three once-off tillage treatments namely: continuous no-till (NT, soil left undisturbed until planting and then planted with an Ausplow), deep tine non-inversion tillage (DT) and mouldboard inversion tillage (MP) were conducted. Tillage treatments were conducted on 26 and 27 May, in 2014 and 2015, respectively. NT treatments were regarded as a control reference for this study. In February 2014 and May 2015, soil samples were taken at 0-50, 50-100, 100-200, 200-300 and 300-400 mm depth increments. Soil water content measurements were taken weekly (during growing season) and monthly (during fallow season) to a depth of 800 mm in order to determine the soil water balance and the resultant crop performance.
The objectives of the study were to investigate the effect of once-off tillage of no-till soil on: i) the soil physical and chemical properties, ii) the soil water balance parameters, (iii) and the resultant crop performance (water use efficiency and rainfall use efficiency) as affected by physical, chemical and soil water balance related properties.
Significant differences in particle size distribution between tillage treatments at different depths were found (P = 0.05). Tillage had no significant effect on coarse fragment percentage in both wheat systems investigated in the study (P = 0.05), although, in the canola after wheat system the DT treatment resulted in a significant higher coarse fragment percentage in the 200-300 mm soil depth (P ≤ 0.05). The general coarse fragment percentage trend observed was an increase with depth. This result is however not indicative of a mechanical sieving action which is usually expected after the repeatable conduction of conventional tillage practices. DT was the only treatment to result in significant aggregate stability decreases in both the WLWC and LWCW crop rotation systems. In the 300-400 mm soil depth (LWCW) a significantly higher aggregate stability was observed for the NT treatment compared to the DT treatment (P = 0.1514) while in the 0-100 mm (WLWC) soil depth a significantly higher aggregate stability was observed for the NT treatment compared to the DT treatment (P = 0.0078). The aggressive mechanical action of the deep tine implement was responsible for the aggregate stability decrease. Aggregate stability decreased with depth and therefore results correlated with SOC results due to increases in aggregate stability percentages in soil depths where increases in SOC were observed. According to results obtained once-off tillage had no significant effect on macro-aggregate density (P = 0.05) and it was concluded that the sample clods used for measurement were not representative of the prevailing soil conditions after tillage conduction. Hydraulic conductivity showed significant differences between treatments. Although not always significant, both the NT and DT treatments showed the highest hydraulic conductivity compared to MP for all cropping systems investigated (P = 0.05). The increase in hydraulic conductivity for the DT treatment can be explained by a more favourable soil structure created by the rip action, while the increase under NT was contributed to the preservation of soil macro-pores which is formed by earthworms and decayed plant roots as well as the present mulch layer. A MP tillage action leaves a soil surface bare which exposes the soil surface to compacting effects of rainfall and soil resettlement.
MP tillage had a significant effect on pH (KCl and H₂O) while DT tillage had no significant effect. Significant differences were however only observed in the 0-50 mm and 50-100 mm soil depth increments (P = 0.05). The general trend was an increase in pH (KCl and H₂O) with depth and therefore it was concluded that differences were not attributed to a tillage effect but rather to the inherent mother material properties. It is well known that mother materials have higher pH values compared to weathered soil materials. A decreasing trend with soil depth was observed for electrical conductivity. DT proved to be the least favourable in terms of the leaching of salts due to EC increases while NT proved to be the most favourable. The SOC content was not influenced by the single tillage operation as no significant differences were observed between all tillage treatments at all measured depths (P = 0.05). The highest SOC content was observed in the 0-100 mm soil depth where after SOC decreased with each measured depth. The Active C content was not significantly influenced by a once-off tillage operation as was expected in 2014 (P = 0.0005). The prevailing low soil temperatures did not allow active microorganism activity. In 2015 (1 year after tillage) a significant increase in active C content (P = 0.0258) was observed for DT for both the medic MP tillage had a significant effect on pH (KCl and H₂O) while DT tillage had no significant effect. Significant differences were however only observed in the 0-50 mm and 50-100 mm soil depth increments (P = 0.05). The general trend was an increase in pH (KCl and H₂O) with depth and therefore it was concluded that differences were not attributed to a tillage effect but rather to the inherent mother material properties. It is well known that mother materials have higher pH values compared to weathered soil materials. A decreasing trend with soil depth was observed for electrical conductivity. DT proved to be the least favourable in terms of the leaching of salts due to EC increases while NT proved to be the most favourable. The SOC content was not influenced by the single tillage operation as no significant differences were observed between all tillage treatments at all measured depths (P = 0.05). The highest SOC content was observed in the 0-100 mm soil depth where after SOC decreased with each measured depth. The Active C content was not significantly influenced by a once-off tillage operation as was expected in 2014 (P = 0.0005). The prevailing low soil temperatures did not allow active microorganism activity. In 2015 (1 year after tillage) a significant increase in active C content (P = 0.0258) was observed for DT for both the medic after wheat and the wheat after canola systems which was explained by an increase in microbe activity due to favourable soil conditions.
Tillage had a negligible small effect on SWC during the 2014 growing season. Significant differences were only observed between NT and DT after big rainfall events and at the end of the growing season (P = 0.05). SWC readings in 2014 ranged between 35-270 mm for all tillage treatments and crop rotation systems measured. ET values varied according to the crops developing stage as well as the available SWC and external environmental factors (rainfall and temperature). Tillage had no significant effect on ET as no significant difference in ΣET was observed at the end of the 2014 growing season (P = 0.05). Tillage had no effect on the ability of the soil to store water during the 2014/2015 fallow season as no significant difference in SWC were observed between treatments. More valuable results would have been obtained during the fallow season if technical difficulties could have been solved. The total amount of rainfall recorded during the 2015 growing season was 31% lower compared to rainfall recorded during 2014 and therefore SWC readings during 2015 ranged between 10-140 mm. Generally, the highest SWC was observed for the MP treatment for all crop rotation systems and on several dates significant higher SWC readings were observed for MP compared to NT and DT (P ≤ 0.05). MP resulted in a significantly higher ΣET at the end of the 2015 growing season (P = 0.05). Due to limited information on the topic a valuable explanation for the higher SWC and ΣET under MP was not found.
In the 2014 growing season no significant differences in wheat yield were found between all tillage treatments and crop rotation systems investigated while for the 2015 growing season NT resulted in a significantly higher wheat yield (P =0.0274) compared to both DT and MP in the CWLW system which was attributed to the crop residues present. Although the lowest biomass was obtained for the MP treatment no significant difference between treatments were observed for medics (P = 0.9010). The lower biomass under medics was contributed to the transportation of the self-regenerating medic seeds during the inversion plough action which resulted in seedling emergence delays and poor crop stand. When comparing the 2014 and 2015 grain yield results a 71% decrease in canola yield was observed while a 57% decrease in wheat grain yield was observed in the 2015 growing season. Even though the crops underwent a longer growing season during 2015 a total of 31% less rainfall was recorded during the 2015 growing season compared to the 2014 growing season and therefore lower grain yields were expected. Once-off tillage had no significant effect on WUE and RUE in both the 2014 and 2015 growing seasons for all tillage treatments and crop rotation systems tested.; AFRIKAANSE OPSOMMING: Bewaringsboerdery word wêreldwyd deur boere aangeneem wie vasgestel het dat enige grondversteuring noodlottig is vir beide grondfisiese en grondchemiese eienskappe. Alhoewel, soos wat die effek van verminderde bewerking en maksimum stoppelbehoud meer opvallend raak, kan sekondêre effekte, positief of negatief, ontwikkel by die grondoppervlak of in die boonste grondlae van die grondprofiel. Daarom het ‘n toenemende belangstelling in strategiese bewerking na vore gekom om sodoende die bewaringsbewerking beperkings te adresseer. Die studie het deel gevorm van ‘n langtermyn proef, gevestig in 2007, wat verskillende gewas/weiding sisteme onder geen bewerking ondersoek by Langgewens Navorsingsplaas van die Departement Landbou Wes-Kaap naby Moorreesburg, Swartland, Suid-Afrika. Die studie is uitgevoer gedurende die 2014 en 2015 groeiseisoen om sodoende die effek van eenmalige bewerking (bewerk eenmalig in 10 jaar) van geen bewerkde grond in langtermyn medic/koring/medic/koring (McKMcK), koring/lupiene/koring/kanola (KLKC) and lupiene/koring/kanola/koring (LKCK), koring/medic/koring/medic (KMcKMc) en kanola/koring/lupiene/koring (CKLK) gewassisteme (die laaste letter in die volgorde verteenwoordig die gewas teenwoordig in die veld by monsterneming). Drie eenmalige bewerkingsbehandelings is uitgevoer naamlik: aanhoudende geen-bewerking (NT, grond onversteur gelaat tot plant en dan word geplant met ‘n Ausplow), diep tand geen omkering bewerking (DT) skaarploeg omkeer bewerking (MP). Bewerkings is uitgevoer op 26 en 27 Mei 2014. Geen bewerkings behandelings is geag as kontrole vir die studie. In Februarie 2014 en 2015 is grondmonsters geneem by 0-50, 50-100, 100-200, 200-300 en 300-400 mm diepte inkremente. Grondwaterinhoud metings is weekliks geneem (gedurende groeiseisoen) en maandeliks (gedurende braakseisoen) tot ‘n diepte van 800 mm om sodoende die grondwaterbalans te bepaal en die resulterende gewasprestasie.
Die objektiewe van die studie was om die effek van eenmalige bewerking van geen bewerkde grond te ondersoek op: i) die grond fisiese en chemise eienskappe soos geaffekteer deur eenmalige bewerking, ii) die grondwaterbalans soos geaffekteer deur eenmalige bewerking, iii) en die resulterende gewasprestasie (waterverbruiksdoeltreffendheid en reënvalverbruiksdoeltreffendheid) soos geaffekteer deur fisiese, chemiese en grondwaterbalans verwante eienskappe na die uitvoer van eenmalige bewerking.
Betekenisvolle verskille in partikelgrootte verspreiding tussen behandelings is gevind (P = 0.05). Betekenisvolle verskille is mees kenmerklik gevind vir die growwe- en fyn sandfraksie en tussen NT en DT behandelings. Bewerking het geen betekenisvolle effek gehad op growwe fragment persentasie in beide koring stelsels (P = 0.05), alhoewel, DT het geresulteer in betekenisvolle hoër growwe fragment persentasies vergelykend met MP en NT behandelings in die 200-300 mm gronddiepte (P ≤ 0.05). Die algemene tendens was ‘n verhoging in growwe fragment persentasie met diepte. Die tendens was alhoewel nie verteenwoordigend van ‘n meganiese siftings aksie wat gewoonlik resulteer na aanhoudende uitvoer van konvensionele bewerkingspraktyke nie. DT het ‘n betekenisvolle effek op aggregaatstabiliteit gehad. DT het in ‘n betekenisvolle laer aggregaatstabiliteit geresulteer vergelykend met NT in die 300-400 mm gronddiepte in ‘n LKCK stelsel (P = 0.1514), asook, DT het ‘n betekenisvolle laer aggregaatstabiliteit gehad vergelykend met NT in die 0-100 mm diepte vir WLWC (P = 0.0078). Aggregaatstabiliteit het verlaag met diepte en daarom korrelleer resultate met grond organiese koolstof (GOK) resultate as gevolg van verhogings in aggregaatstabiliteit persentasies in gronddieptes waar verhogings in GOK opgemerk is. Eenmalige bewerking het geen betekenisvolle effek op makro-aggregaat digtheid gehad nie (P = 0.05). Daar was tot die gevolgtrekking gekom dat kluitmonsters nie ‘n aanduiding was van die heersende grondkondisies soos na bewerking te verwagte is nie. Hidrouliese geleiding het betekenisvolle verskille tuseen behandelings getoon. Alhoewel nie altyd betekenisvol verskillend nie, het beide NT en DT behandelings die hoogste hidrouliese konduktiwiteit getoon vergelykend met MP vir alle stelsels betrokke (P = 0.05). Die verhoging in hidrouliese konduktiwiteit kan toegeskryf word aan ‘n meer gunstige grondstruktuur geskep deur die tandaksie, terwyl die verhoging onder NT toegeskryf word aan die preservering van die grond se makroporieë gevorm der erdwurms en verotte plantwortels asook die teenwoordigende restelaag. Die MP bewerking laat die grond naak na bewerking wat die grond blootstel aan partikel hervestiging en konsolidasie onder die invloed van reënval.
MP het ‘n betekenisvolle effek op pH (KCl and H₂O) gehad terwyl DT geen betekenisvolle effek getoon het nie. Betekenisvolle verskille is slegs waargeneem in die 0-50 mm en 50-100 mm diepte. Die algemene tendens was ‘n verhoging in pH (KCl en H₂O) met diepte en daarvoor is daar tot die gevolgtrekking gekom dat verskille nie toegeskryf is aan bewerking nie maar eerder die teenwoordigende moedermateriaal. Dit is welbekend dat moedermateriale hoër pH’s besit as verweerde grondmateriale. ‘n Verlagende tendens met gronddiepte is opgemerk vir elektriese konduktiwiteit (EC). DT het bewys om ongunstig te wees ten opsigte van loging van soute as gevolg van EC verhogings terwyl NT die meeste gunstig was vir die doel.
Die GOK inhoud was nie beinvloed deur die enkele bewerkingsoperasie nie omdat geen betekenisvolle verskille met diepte opgemerk is nie (P = 0.05). Die hoogste GOK inhoud is gesien in die 0-100 mm gronddiepte waar GOK met elke gemete diepte verlaag het vir alle behandelings. Die aktiewe koolstof inhoud was nie betekenisvol beinvloed deur ‘n eenmalige bewerkings operasie nie soos wat te verwagte was in 2014 as gevolg van heersende koue grondtemperature wat mikro organisme aktiwiteit vertraag (P= 0.0005).
In 2015 (1 jaar na bewerking) is ‘n betekenisvolle verhoging in aktiewe koolstof opgemerk (P = 0.0258) vir DT in beide medic na koring en koring na canola stelsels as gevolg van ‘n verhoging in mikrobe aktiwiteit as gevolg van gunstige grondkondisies.
Bewerking het ‘n weglaatbare klein effek gehad op grondwaterinhoud (GWI) die 2014 groeiseisoen. Betekenisvolle verskille is gesien tussen NT en DT na groot reënval gebeurtenisse en aan die einde van die groeiseisoen (P = 0.05). GWI lesings in 2014 het gevarieër tussen 35-270 mm vir alle bewerkingsbehandelings en gewasrotasiestelsels. Bewerking het geen betekenisvolle effek op ET gehad anngesien geen betekenisvolle verskil in ΣET opgemerk is aan die einde van die 2014 groeiseisoen (P = 0.05). Geen betekenisvolle verskil tussen bewerkingsbehandelings is opgemerk gedurende die 2014/2015 braakseisoen. Die totale hoeveelheid reënval opgeneem gedurende die 2015 groeiseisoen was 31% laer as die hoeveelheid opgeneem gedurende 2015. Die hoogste GWI is opgemerk vir die MP behandelings vir alle gewasrotasiesisteme en op verskeie datums is betekenisvol hoër GWI lesings opgeneem vir MP (P = 0.05). MP het geresulteer in ‘n betekenisvol hoër ΣET aan die einde van die 2015 groeiseisoen (P = 0.05). As gevolg van ‘n tekort aan navorsing oor die onderwerp is geen verklaarbare rede gevind vir die hoë waterinhoud en ΣET onder MP.
In die 2014 groeiseisoen is geen betekenisvolle verskil gevind tussen bewerkingsbehandelings en gewasrotasiestelsels ondersoek terwyl daar in die 2015 groeiseisoen ‘n betekenisvolle hoër opbrengs opgeneem is vir NT in die CKLK stelsel (P = 0.9010). Alhoewel die laagste biomassa vir MP opgeneem is is geen betekenisvolle verskil gevind in biomassa resultate nie (P = 0.0274). Wanneer die 2014 en 2015 resultate vergelyk word is ‘n 71% verlaging in opbrengs resultate vir kanola opgemerk terwyl ‘n 57% verlaging in koring graanopbrengs opgemerk is in 2015. Eenmalige bewerking het geen betekenisvolle effek gehad op waterverbruiksdoeltreffendheid en reënvalverbruiksdoeltreffendheid in beide 2014 en 2015 vir alle bewerkingsbehandelings en gewasrotasiestelsels ondersoek.
Thesis (MSc)--Stellenbosch University, 2016.
2016-03-01T00:00:00ZMitigation of soil and ground water pollution caused by on-land disposal of olive mill wastewaterhttp://scholar.sun.ac.za:80/handle/10019.1/98774
Mitigation of soil and ground water pollution caused by on-land disposal of olive mill wastewater
Umeugochukwu, Obiageli
ENGLISH ABSTRACT: Olive mill wastewater (OMW) is generated in large quantities, particularly in the regions with a Mediterranean climate where olive oil is produced on a commercial scale. Some producers collect the effluent and dispose of it as hazardous waste at significant expense, while others dispose of it directly on land, claiming the potential benefits to productivity from the plant nutrients present in the OMW. It was shown that the OMW also contains some phytotoxic phenols, which may have both immediate and cumulative negative effects on plant growth. The long-term effects on the soil and crop growth have been shown to be detrimental. Sandy soils are of particular concern due to the possibility of phenol penetration into deeper soil layers and potential ground water contamination.
The study explores in-situ (soil amendment with biochar prior to the OMW disposal) and ex-situ (OMW filtration through a biochar bed) options to mitigate the negative effects of the OMW on-land disposal.
A laboratory batch sorption experiment was set up using 0.2 g pinewood biochar to explore the possibilities of removing the phenols from 50 mL of the OMW or gallic acid (GA) solutions at different concentrations. The results showed that the sorption process was rapid and stabilized within one hour. The kinetic process followed a pseudo-second-order model and was described by the Freundlich multi-layer isotherm. The pinewood biochar had a sorption capacity of 30 mg·g-1 and 100 % removal was obtained with 300 g·l-1 of the OMW load. It was found that pinewood biochar could be used to remove the phenols contained in the effluent.
A column experiment was set up to determine the effectiveness of biochar and biochar-soil mixtures in removal of phenol and Chemical Oxygen Demand (COD) from the OMW compared to sand filtration. The breakthrough curves for phenol and COD were determined, while the pH and EC of the filtrates were monitored. Ten PVC columns of 30 cm height and 5 cm diameter were filled with five different materials: sand, sand + biochar, Hutton clay loam soil, Hutton clay loam soil + biochar and biochar alone. Two different treatments were given to the columns; five of the columns were prewashed with 2 liters of deionized water and the other five were not washed before the OMW filtration. The performance of the columns was determined in respect of the phenol and COD removal capacities, hydraulic conductivities and porosity changes. The results showed that washing enhanced the phenol sorption but not the COD sorption. The addition of the biochar at 2%wt load significantly improved the effectiveness of the filtration. The best performance was achieved in terms of COD removal in pure biochar columns, but in terms of the phenol, the best performance was on a pre-washed Hutton clay loam soil with 2%wt biochar addition. Both the washing and biochar addition affected the porosity and reduced the hydraulic conductivity of the columns.
The greenhouse experiments were conducted to confirm the above statement using pot trials laid out in a 4 x 4 factorial Randomized Complete Design (CRD) to determine the effect of effluent and biochar on wheat and green beans on alkaline sand. Results showed that the increasing effluent rate up to 200 m3·ha-1 gave significantly negative results on wheat growth, even with fertilizer application. But the effect was different for beans where low effluent loads gave positive results though not significant while with fertilizer (N and P) 50 m3·ha-1 performed better. With the addition of biochar there was no significant effect on wheat, but it significantly affected beans at the application rate of 2.5 and 5%wt. The interaction of biochar and effluent showed that the best performance was at 5% biochar application and effluent loads of 50 and 100 m3·ha-1, but increased effluent rate decreased production even with a 5% wt biochar application rate. It was suggested that a leguminous crop should tolerate OMW application better compared to wheat even in the adverse conditions of the alkaline sand.
A second greenhouse experiment was conducted with another legume, an indigenous African crop, the bambara groundnut, on an acidic Hutton clay-loam soil (Oxisol) sourced locally. The experiment was laid out in a 2 x 6 CRD factorial design to determine the effect of the biochar and effluent combination on the yield and growth parameters of bambara as well as the effect on soil conditions and nutrient availability. The result showed that biochar addition improved seed germination, which was retarded by effluent loading. The effluent rate of 200 m3·ha-1 and biochar 2% gave the best yield performance. The biochar addition increased the pH and hence affected the release of P and N whereas Na and K availability were reduced.
We conclude that biochar may be used for both ex-situ filtration to treat the OMW, and as a soil amendment to allow safe on-land disposal of the OMW. The estimations of safe disposal loads and the required application rates of the biochar should be made individually for a specific soil type. Pinewood biochar was proven to be a cheaper source of activated carbon for the treatment of olive mill wastewater organic contaminants in South Africa.; AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar
Thesis (PhD)--Stellenbosch University, 2016.
2016-03-01T00:00:00Z